Process for eliminating unstable hydrogen from lubricating oil stock

ABSTRACT

A stabilized lubricating oil resistant to oxidation and sludge formation upon exposure to a highly oxidative environment, such as when metals are present and an overbased component is present in the lubricating oil, is formed by contacting the lubricating oil stock with a small amount of elemental sulfur of from about 0.2 to about 1.0 percent by weight in the presence of a catalyst material selected from the group consisting of alumina, a siliceous material, an aluminosilicate, a metal of Groups II-A, II-B, VI-B or VIII of the Periodic Table of Elements, an oxide of a metal of Groups II-A, II-B, VI-B or VIII, a sulfide of a metal of Groups II-A, II-B, VI-B or VIII, clay and combinations thereof, at relatively low temperatures of from about 130*C to about 250*C, said catalyst material being present in amount of from about 2 to about 15 parts by weight per 100 parts by weight of said oil stock.

United States Patent [191 Heiba et al.

[ 51 Sept. 9, 1975 [75] Inventors: El-Ahmadi Ibrahim Heiba,

Princeton; Robert Frederick Bridger, Hopewell, both of NJ.

[73] Assignee: Mobil Oil Corporation, New York,

22 Filed: Oct. 5, 1973 21 App]. No.: 404,070

[52] U.S. Cl. 208/177; 208/288; 208/295; 208/296; 208/299 [51] Int. Cl... Cl0g 29/02; ClOg 29/04; ClOg 29/10 [58] Field of Search 208/177, 208, 209, 213, 208/18, 243, 244, 245, 247, 249, 250, 293,

[56] References Cited UNITED STATES PATENTS 2,130,024 9/1938 Pier ct al. 208/18 2,790,751 4/1957 Gerald 208/250 Primary Examiner-Delbert E. Gantz Assistant ExaminerG. J. Crasanakis Attorney, Agent, or Firm-Charles A. Huggett; Raymond W. Barclay; Dennis P. Santini [5 7] ABSTRACT A stabilized lubricating oil resistant to oxidation and sludge formation upon exposure to a highly oxidative environment, such as when metals are present and an overbased component is present in the lubricating oil, is formed by contacting the lubricating oil stock with a small amount of elemental sulfur of from about 0.2 to

about 1.0 percent by weight in the presence of a catalyst material selected from the group consisting of alumina, a siliceous material, an aluminosilicate, a metal of Groups ll-A, ll-B, VI-B or VIII of the Periodic Table of Elements, an oxide of a metal of Groups ll-A, ll-B, Vl-B or Vlll, a sulfide of a metal of Groups ll-A, Il-B, Vl-B or Vlll, clay and combinations thereof, at relatively low temperatures of from about 130C to about 250C, said catalyst material being present in amount of from about 2 to about 15 parts by weight per 100 parts by weight of said oil stock.

8 Claims, N0 Drawings PROCESS FOR ELIIVIINATING UNSTABLE HYDROGEN FROM LUBRICATING OIL STOCK BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to the production of improved lubricating oils. In particular, it relates to the preparation of stable lubricating oils which are highly resistant to oxidation and sludge formation when exposed to a highly oxidative environment.

2. Description of Prior Art Hydrocarbon lubricating oils have been obtained by a variety of processes in which high boiling fractions are contacted with hydrogen in the presence of hydrogenation-dehydrogenation catalysts at elevated temperatures and pressures. In such processes, there is a consumption of hydrogen. Lubricating oil fractions are separated from the resulting products. Such lubricating oil fractions differ from those obtained by fractional distillation of crude oils and the like, since they have such relatively high viscosity index values that solvent extraction treatments are generally not required to enhance their viscosity index values. Such lubricating oil fractions suffer from the shortcoming that they are unstable when exposed to highly oxidative environments. When so exposed, sediment and lacquer formation occurs, thus lessening the commercial value of such lubricants.

Methods in the art directed to lessening such a shortcoming are exemplified by US. Pat. Nos. 3,436,334 and 3,530,061. They teach making a lubricating oil product fraction of hydrocracking resistant to deterioration upon exposure to light and air by contacting the lubricating oil fraction with a solid contacting agent having hydrogenation-dehydrogenation properties under hydrogen pressure (U.S. Pat. No. 3,530,061); and making hydrocarbon lubricating oil resistant to such deterioration by contacting high boiling hydrocarbons with a hydrogenation-dehydrogenation catalyst and hydrogen (with hydrogen consumption), and thereafter dehydrogenating the resultant product on contact with a metal oxide or with metal and oxygen (U.S Pat. No. 3,436,334). Both methods employ hydrogen atmosphere, high pressure and high temperature, i.e. 500 to lOF. No sulfur is employed in either patent method.

The present invention is directed to a process and means for effecting substantial improvement in oxida- -tive properties of lubricating oil by a low pressure, relatively low temperature partial dehydrogenation mechanism in the presence of a small amount of elemental sulfur and a catalyst.

US Pat. No. 2,604,438 teaches a hydroforming process for catalytic dehydrogenation of light (i.e. boiling at less than 600F) hydrocarbon oils, presumably to increase aromatic content. The patent discloses the known fact that in processes of that nature, the presence of a small amount of sulfur in the feed has a beneficial effect. It further states that when the oil to be hydroformed" has no sulfur, i.e. no sulfur in the light hydrocarbon feed, then a small amount of sulfur, e.g., a reducible sulfur compound, is added to the feed. The patent emphasizes that the invention disclosed therein is only advantageous when the process is carried out at a temperature conducive to dehydrogeneration, i.e., at a temperature of at least 825F. Proclaimed in the patent is the fact that when lower temperatures are used, e.g. to 250C as in the present invention, the described method offers no advantage.

The prior art practices of hydrofinishing and hydrotreating as a means of treatment of lubricating oil stocks (i.e. stocks boiling at temperatures over 600F) leave behind the unstable oil fractions, i.e., hydroaromatic compounds, with labile hydrogen atoms such as, for example, fluorenes, benzofluorenes, acenaphthenes, tetralin, fused cycloalkylaromatics and naphthenes, which are quite unstable toward oxygen, particularly in the presence of metals in lubricating oil formulations containing overbased additives. These hydroaromatic compounds with labile hydrogen atoms are known to be present in small quantities in conventionally furfural refined stocks and can lead to oxidative instability of any lubricant containing them. Further, it is well known that the sensitivity of certain lubricating oils toward alkaline additives can cause oxidative degradation in applications where overbased additives are used, such as automotive and diesel lubricants. Also, metal sensitivity can be quite detrimental to the oxidative stability of lubricants or functional fluids in applications such as turbine circulating oils, steam turbine oils and hydraulic fluids. No method is known at present which so effectively and easily alleviates the above problems as the present invention.

SUMMARY OF THE INVENTION In accordance with the present invention there is provided a process and means for forming lubricating oils which are highly resistant to deterioration, e.g. oxidation and sludge formation, upon exposure to a highly oxidative environment.

The process of the present invention comprises contacting a lubricating oil stock, such as, for example, from a Midcontinental U.S.A. crude or an Arabian Light crude, with elemental sulfur in amount of from about 0.2 to about 1.0 percent by weight of the oil stock in the presence of a catalyst material selected from the group consisting of alumina, a siliceous material, an aluminosilicate, a metal of Groups II-A, ll-B, VI-B or VIII of the Periodic Table of Elements, an oxide of a metal of Groups II-A, Il-B, VI-B or VIII, a sulfide of a metal of Groups II-A, II-B, VI-B or VIII, clay and combinations thereof one with the other.

The elemental sulfur for use herein may be provided for the treatment, if desired, by a sulfur precursor, such as, for example, H S, an organosulfur compound, i.e. added or naturally occurring, or combinations thereof. Said naturally occurring organosulfur compound may be utilized if present in the lubricating oil stock in a quantity providing greater than about 0.3 weight percent sulfur. When such an organosulfur compound is the source of elemental sulfur herein, it can serve for generation of sulfur in situ. The catalyst materials for use in this invention serve to assist the extrusion of naturally occurring sulfur from the lubricating oil stock and, if sufficient organosulfur compounds are present therein, dehydrogenation is enhanced.

Non-limiting examples of sulfur precursors which may be utilized in the present process include H 5, RSH, RS I-I, HS H, and RS R, wherein R is a hydrocarbyl group and x is an integer of from 1 to 4 or more. Under actual operating conditions as herein set forth, these sulfur precursors, if used, can interact with the catalyst material for use herein to serve as a source of active sulfur in situ.

The treatment in accordance-with the present invention may be followed, if desired, with various well known treatments such as thermal treatment or oxidation treatment in the presence of atmospheric oxygen and transition metal ions.

DESCRIPTION OF SPECIFIC EMBODIMENTS The lubricating oil stock which may be treated in accordance with the present invention may generally be any high boiling range materials boiling above about 600F. Such lubricating oil stock materials include those obtained byfractionation, as by, for example, vacuum distillation, of crude oils identified by their source, i.-e. Pennsylvania, Midcontinent, Gulf Coast, WestTexas, Amal, Kuwait, Barco and Arabian. Said oil stock material may be one havinga substantial part thereof of the fractionation product of the above crude oils mixed with other oil stocks. a

The catalyst materials employed herein can include any type of catalyst which will bring about partial dehydrogenation and. sulfur labilization (or sulfurizationdesulfurization) when applied to the lubricating oil stock in the presence of elemental sulfur in small quantityand at low operating temperature in an unpressured system. Such catalyst materials are known in the art for use in various other catalytic processes and include alumina, a siliceous material such as, for example, silica or silica-alumina, an aluminosilicate, a metal of Groups Il-A, II-B, Vl-B or VIII of the Periodic Table of Elements, such as, for example, Mg, Ca, Zn, Cr, Mo, Fe, Co, Ni or Pt, an oxide of a metal of Groups II-A, Il-B, Vl-B or VIII such as CaO, MgO, Fe O MnO Cr O or ZnO, a sulfide of a metal of Groups II-A, II-B, VI-B or VIII such as, for example, Fe S, Fe- S FeS- (either marcasite or pyrite) or Fe S, (pyrrhotite), certain clay and combinations thereof.

Non-limiting examples of the clays which may be usefulas the catalyst material in the process of this invention includethe montmorillonite and kaolin families, which families includethesub-bentonites and the kaolins "commonly known as Dixie, McNamee, Georgia and Florida clays, or others in which the main mineral constituent is halloysite, kaolin, dickite, nacrite, attapulgite or'anauxite. Such clays can be used in the raw state as mined-orinitially subjected tocalcination, acid treatment or chemical modifications.

- Non-limiting examples of siliceous materials useful as the catalyst in the present invention include silica and combinationsthereof with oxides of metals of Groups lI-A, IIIA, IV-B and V-B, such as, forexample, silicaalumina, silica-magnesia, silica-zirconia, silica-thoria, silica-beryllia, silica-titania, as well as ternary compositions'of silica,-such as, for example, silica-aluminathoria and silica-aluminazirconia'.

Non-limiting examples of aluminosilicate materials spheric to about 500 pounds per square inch, a total gas flow rate of from about 1 to about volumes per volume of catalyst per minute and an oxygen concentration of from about 0.1 percent to 100 percent. The oxygen can be diluted with steam, nitrogen or other inert gas. v

The process of the present invention involves the partial incorporation of sulfur into the lubricating oil stock or the partial desulfurization of the oil stock in addition to the partial dehydrogenation of the oil stock.,Said dehydrogenation is believed to involveoxidatively unstable fractions of said oil stock including, for example, the above mentioned hydroaromatics such as fluorenes, .benzofluorenes, acenaphthenes, tetralin, fused cycloalkylaromatics, naphthenes and the like. The unstable hydrogen of said hydroaromatics is eliminated psig. The sulfur in such an embodiment of the present from theoil stock treated in accordance herewith as one or more of the forms I-I S, RSI-I, HS I-I and RS R, wherein R is a hydrocarbyl group of xis an integer ranging from 1 to'about 4 or more. I

The elemental sulfur employed in. the process of the present invention may be in any of several allotropic forms such as S 5,, or polymeric sulfur, and may be used in small amounts of from about 0.2 to about 1.0 percent by weight of oil stock, with a preferable range of from about 0.5 to about 0.7 percent by weight. It is readily observable that this invention differs from the well-known method of making sulfurized oil-extreme pressure agents in conditions of processing, the concept of improvement, the amount and'type-of sulfur imcorporated and the chemical modification of the oil stock itself. In the present invention, small amounts of stable sulfur may be chemically incorporated into the oil molecules as labile hydrogen atoms are removed. On' the other hand, in sulfurized oils used as extreme pressure agents, large quantities of sulfur, such as, for example, 10 to 15 percent by weight, are incorporated, including a substantial quantity of-elemental sulfur as such.

If desired in the present process, and specifically if desired when the lubricating-oil stock being treated in accordance herewith contains substantial naturally occurring organosulfur compounds such that the sulfur content of the oil is greater than about 0.3 weight percent, a low partial pressure of hydrogen may be applied to the catalyst-oil system of from about 15 to about 250 invention is provided in situ as hereinbefore described andthe lubricating oil product is substantially im-' proved in stability properties.

In practice of the present invention, a base or base v precursor may be used as a secondary agent in combiwhich may be useful as the catalyst herein include the v The catalyst loses some of its activity during use and,

therefore, may'be regenerated. The spent catalyst is contacted with a free oxygen-containing atmosphere at an elevated temperature sufficient to burn carbona-.

ceous deposits from the catalyst. Conditions for regenerating the catalyst include a temperature between nation with the catalyst as above defined. Non-limiting examples of, such secondary agents include lithium hydroxide, potassium hydroxide, potassium acetate, sodium hydroxide, sodium acetate and sodium carbonate. Such a combination of catalyst material and secondary agent promotes the fixing of sulfur and/or the dehydrogenation of labile hydrogen atoms.

The operating parameters in the-present process are critical to achieving the desired result of degree of improvement-or upgrading product quality of the lubricating oil stock treated without loss in yield. Aside from specific. small amounts of sulfur, the amount of catalyst material used should be between about 2 and about l5 parts by weight per parts by weight of oil stock treated with about 3 to about parts preferred. The temperature of the process must be within the range of from about 130 to about 250C, with a preferred range of from about 150 to 210C.

In order to more fully illustrate the process of the present invention, the following specific examples, which in no sense limit the invention, are presented. The basic test procedure employed in evaluation of product yield from the present process is described in U.S. Pat. Nos. 3,287,270; 3,320,165; 3,415,749; 3,634,238 and 3,665,038. Three separate modifications of the basic test procedure were used in the following examples, as described below with identification as Test Method A," Test Method B and Test Method C, to be used in reference thereto hereinafter.

It is interesting to note that performance of a lubricating oil in the below described test methods is clearly indicative of that oils performance in the field.

Test Method A. This test is conducted in an oxygen circulation apparatus of the type described by Dornte (Ind. Eng. Chem.,28, 26-30, 1936) modified so the rate of oxygen absorption can be recorded automatically. In general, a tube containing 30 grams of lubricating oil (with or without additive) is placed in a heater thermostatted at 175C. After thermal equilibrium is established, the sample tube is connected with the closed oxygen circulation system. Oxygen is circulated through a fritted glass disk near the bottom of the sample tube at the rate of 5 liters per hour. The time in hours required for the absorption of 1 mole of oxygen per kilogram of sample is taken as the inhibition period. The

-longer the inhibition period, the greater is the oxidation resistance of the sample.

Test Method B. This test is conducted using the same apparatus as described above. The temperature of the test is 162C, and metal surfaces are employed as oxidation accelerators. Air (instead of oxygen) is circulated through the sample at a rate of 5 liters per hour. The metal surfaces employed as oxidation accelerators include: iron wire, analytical grade, Washburn and Moen No. gage, wound into a coil approximately Test Method B in a constant temperature bath at 162C. Air is passed through the oil at a rate of 10 liters per hour for 40 hours. At the end of the test period, the changes in neutralization number (ANN) and kinematic viscosity at 210F (AKV) were determined to measure the oxidative degradation of the oil. The larger the value of ANN and AKV, the greater the deterioration of the oil.

Because of the fact that many lubricating oils, and especially Midcontinental stocks, are particularly unsta ble towards atmospheric oxidation in the presence of overbased additives or metal catalysts, most samples were tested by Test Method A with 1 percent overbased calcium phenate admixed with the sample. Overbased alkaline additives such as this are used widely in lubricating oil compositions for automotive and diesel applications. The overbased calcium phenate used here had a total base number of 300 (titration'value, mg. KOH/gm. sample) and was of the type shown below:

wherein x, a number dependent on the degree of overbasing, was approximately 1.3.

The lubricating oil stocks used in the following examples were conventionally refined by distillation, followed by furfural extraction and methyl ethyl ketone dewaxing. They are identified in Table 1 according to source of their crude oil, physical properties and furfural extraction conditions.

TABLE 1 CRUDE SOURCE AND NOMINAL VISCOSITY OF LUBRICATING OIL STOCKS USED HEREIN I00 S.U.S. Z00 S.U.S. I S.U.S. Midcontinental Midcontinental Arabian Light Furfural Dosage, "/1 volume 150 I 180 Tower Tcmp., F, Top 220 230 185 Tower Temp., F, Bottom I 200 140 Gravity, API 31.5 30.0 30.9 Pour Pt. F 5 5 0 Flash PL, F 390 425 410 Sulfur, 7( wt. 0.30 0.27 0.63 Nitrogen, 7( wt. 0.006 0.007 0.0029 Aniline Point, F 208.8 2l9.l 2l0 Viscosity, S.U.S. at l00F I25 232 I52 Viscosity Index 98 97 103 ASTM Color IV: l /z IV;

inch O.D. and 2 /8 inches long to give a surface area of 60 EXAMPLE 1 approximately 15.3 square inches; copper wire, electrolytic, B and S gage N0. 18, 6.2 inches long; and a lead (tin-free) square 0.25 inch X 0.25 inch cut from from 1/16 inch thick sheet.

Test Method C. This test is conducted by thermostatting a tube containing 30 grams of the lubricating oil and the iron, copper, and lead catalysts described in A 200 gram quantity of the 100 S.U.S. Midcontinental stock was subjected to Test Method A defined above and another quantity to Test Method B defined above, each quantity without treatment in accordance to the present'invention. The results of the tests are recorded in Table 2 for comparison purposes with results of tests conducted on the same oil stock treated by present process (Examples 2 and 3).

EXAMPLE 2 e A 200 gram quantity of the 1 S.U.S. Midcontinental stock was th'ermo'statted under nitrogen at 200C in the presence of grams of alumina impregnated with iron sulfide (10 percent on alumina). Sulfur 1.4 grams) was added and the oil was stirred at 200C for 2 hours while hydrogen sulfide was evolved. The oil was cooled to room temperature and residual corrosive sulfur was removed by stirring the oil with finely divided sodium hydroxide (8 grams) for 32hours. After removal of the sodium hydroxide by filtration, the oil was tested by Test Methods A and B, and shown to have improved oxidation properties, as shown in Table 2. l

EXAMPLE 3 A 200 gram quantity of the 100 S.U.S. Midcontinen- EXAMPLE 4 A 200 gram quantity of the 200 S.U.S. Midcontinental stock was subjected to Test Method A defined above and another quantity to Test Method B defined above, eachlquantity without treatment in accordance to the presentinvention. The results of the tests are re corded in'Table 2 for comparison purposes with results of tests conducted on the same oil stock treated by the present process (Examples 5-10).

EXAMPLE 5 The 200 S.U.S. Midcontinental Stock was treated under the conditions described in Example 3, except that a reaction time of 1 hour was used. The resulting improvement in the oxidative stability of the oil is shown in Table 2;

EXAMPLE 6 The 200 S.U.S. Midcontinental stock was treated under the conditions of Example 5, except that the reaction was increased from 1 hour to 2 hours. The resulting improvement is shown in Table 2.

EXAMPLE 7 The 200 S.U.S. Midcontinental stock was treated in the same manner as in Example 6, except the reaction temperature was lowered from 175 to 165C. The resulting improvement is shown in Table 2.

EXAMPLE 8 The 200 S.U.S. Midcontinental stock was treated in the same way as in Example 6 except that the reaction temperature was raised from 175 to 200Ca-The-resulting improvement is shown inTable 2 EXAMPLE 9 I The 200 S.U.S. Midcontinental stock was treated in the same way as in Example 2 (200C with iron sulfide on alumina). The resulting improvement is shown in Table 2.

EXAMPLE 10 The 200 s.u.s. Midcontinental stock was treated in the same way as in Example 6 except that the amount of sulfur was reduced to 0.24 gram for 200 grams of oil. The improvement in oxidation properties is shown in Table 2. i 7

EXAMPLE .1 l

A 200 gram quantity of the S.U.S. Arabian Light stock was subjected to Test Method A and another quantity to Test Method B, both tests defined above, each quantity without treatment in accordance to the present invention. The results of the tests are recorded in Table 2 for comparison purposes with results of tests conducted on the same oil stock treated by the present process (Examples 12 and 13).

EXAMPL 1 2 The 150 S.U.S. Arabian Light stock was treated in the same way as described in Example 3, except that a 1 hour reaction timewas used. The resulting improvement is shown in Table 2.

EXAMPLE 13 The 150 S.U.S.- Arabian Light stock was treated in the same way as describedin Example 3. The resulting improvement is shown in Table 2 EXAMPLE "i4 The 200 S.U.S. Midcontinental stock was treated under the conditions described; in Example 3, except that 4A zeolite wasusecl as the catalyst. The resulting improvement is shown in Table 2..

EXAMP E 15 The 200 S.U.S. Midcontinental stock was treated under the conditions described in Example 3, except that HZSM-S zeolite was used as the catalyst. The re sulting improvement is shown in Table 2.

EXAMPLE 16 The 200 S.U.S. Midcontinental' stock was treated under the conditions described in Example 3, except that a catalystmaterial of silica was used in combina tion with the secondary agent sodium hydroxide in the ratio 9 parts silica: ,1 part sodium hydroxide. The resulting improvement is shown in Table 2.

EXAMPLE 1 7 The 200 S.U.S. Midcontinental stock was treated under the conditions described in Example 3, except that zinc oxide was used as the catalyst. The resulting improvement is shown in Table '2.

' EXAMPLE 1:;

previously loaded with 0.19 percent of elemental sulfur. The resulting improvement is shown in Table. 2.

EXAMPLE 19 TABLE 2 EXAMPLE 24 The 200.s.u.s. Midcontinental oil was treated as in Example 22;except'that the temperature was raised to 250C. The resulting improvement is shown in Table 3.

EXAMPLE 25 A 200 gram quantity of the 200 S.U.S. Midcontinental stock was theremostatted under nitrogen at 300C OXIDATION RESULTS OF EXAMPLES Time required for the absorption of l mole per kg. of oil (hours) Test Method A with W: Overbased Example Oil Stock Calcium Phenate Added Test Method B l 100 S.U.S. Midcontinental l4 l9 2 I00 S.U.S. Midcontincntal 34 4| 3 100 S.U.S. Midcontinental 24 42 4 200 S.U.S. Midcontincntal l2 8 5 200 S.U.S. Midcontinental 48 6 200 S.U.S. Midcontincntal 56 7 200 S.U.S. Midcontincntal 20 47 8 200 S.U.S. Midcontincntal 41 58 9 200 S.U.S. Midcontinental 26 5] I0 200 S.U S. Midcontinental I4 20 l 1 I50 S.U.S. Arabian Light 17 43 I2 I50 S.U.S. Arabian Light 29 79 13 150 S.U.S. Arabian Light 33 7] I4 200 S.U.S. Midcontinental 25 31 I5 200 S.U.S. Midcontinental 24 I6 200 S.U.S. Midcontincntal 44 I7 200 S.U.S. Midcontinental 25 18 200 S.U.S. Midcontinental 42 19 200 S.U.S. Midcontinental 50 EXAMPLE 20 A gram quantity of the 100 S.U.S Midcontinental stock was subjected to Test Method C defined above, without treatment in accordance to the present invention. The results of the test are recorded in Table 3 for comparison purposes with results of tests conducted on the same oil stock treated according to the present process.

EXAMPLE 2 l A 30 gram sample of the 200 S.U.S. Midcontinental stock was subjected to Test Method C defined above,

without treatment in accordance to the present invention. The results are recorded in Table 3 for comparison with results of tests conducted on the same oil stock treated according to the present process.

EXAMPLE 22 This example shows that a lubricating oil can be upgraded by utilizing as a dehydrogenating agent the sulfur precursors naturally present in the oil. A 200 gram quantity of the 200 S.U.S. Midcontinental oil was passed over sodium faujasite (13X zeolite) in a fixed bed reactor at 175C and liquid hourly space velocity of 0.5. The oil was tested by Test Method C. The resulting improvement is shown in Table 3.

EXAMPLE 23 The 200 S.U.S. Midcontinental oil was treated in Example 22, except that the temperature was raised to 200C. The resulting improvement is shown in Table 3.

with stirring in the presence of 4 grams of platinum-onalumina catalyst (0.5 percent platinum) for 6.5 hours. The oil was cooled to room temperature and the catalyst was removed by filtration. The oil was tested by Test Method C. The resulting improvement is shown in Table 3.

EXAMPLE 26 A 200 gram quantity of the 200 S.U.S. Midcontinental stock was treatedunder the conditions described in Example 25 except that the temperature was raised to 350C, and the reaction time was 4.3 hours. The resulting improvement is shown in Table 3.

EXAMPLE 27 EXAMPLE 28 The 200 S.U.S Midcontinental stock was treated under the conditions described in Example 3, except that the reaction was conducted in a hydrogen atmosphere at ambient pressure (15 psi absolute). The resulting improvement is shown in Table 3.

EXAMPLE 29 The 200 S.U.S. Midcontinental stock was treated under the conditions described in Example 28, except that alumina impregnated with chromium (5 percent chromium) was used as the catalyst. The resulting improvement is shown in Table 3.

EXAMPLE The 200 S.U.S. Midcontinental stock was treated under the conditions described in Example 29, except. that a nickel-molybdenum-on-alumina catalyst (7.7 percent molybdenum and 2.6 percent nickel) was used. The resulting improvement is shown in Table 3.

TABLE 3 silica, at a reaction'temperature of from about 130 to about 250C with evolution of hydrogen sulfide, said catalyst material being present in amount of from about 2 to about 15 parts by weight per 100 parts by weight of said oil stock. i

2. The process of claim l wherein said oil stock has a boiling range of above about 600F.

3. The process of claim 2 wherein said elemental sulfur is present in amount of from about 0.5 to about 0.7

percent by weight of said oil stock, said reaction tem- I perature is from about 150 to about 210C, and said catalyst material is present in amount of from about 3 to about 15 parts by weight per 100 parts by weight of said oil stock.

OXIDATION RESULTS OF EXAMPLES BY TEST METHOD C Change in Acid Number Change in Viscosity Having thus given a general. description of the process and means of this invention and provided by way of examples specific embodiments thereof, it is to be understood that no undue restrictions are to be imposed by reason thereof, and minor modifications may be made thereto without departing from the scope thereof. i

What is claimed is:

l. A process for forming a stabilized lubricating oil resistant to oxidation and sludge formation upon exposure to a highly oxidative environment which comprises contacting a high boiling hydrocarbon fraction lubricating oil stock with elemental sulfur, said sulfur being added in an amount of from about 0.2 to about 1.0 percent by weight of said oil stock, said contacting including a catalyst material selected from the group consisting of a crystalline aluminosilicate zeolite, an amorphous sodium aluminosilicate, an oxide of a metal of Group B of the Periodic Table, alumina containing metals of Groups VI-B, VIIl or combinations thereof, alumina containing a sulfide of a Group VIII metal, and

4. The process of claim 1 wherein said contacting is in the presence of said catalyst material in conjunction with a secondary agent selected from the group consist ing of bases.

7. The process of claim 2 wherein said oil stock comprises at least a substantial part of one obtained by fractionation of a crude oil identified as Pennsylvania, Midcontinent, Gulf Coast, West Texas, Amal, Kuwait, Barco or Arabian.

8. The process of claim 1 wherein said oil stock is one obtained by fractionation of crude oil identified as Midcontinent or, Arabian.

UNITED STATES PATENT AND TRADEMARK OFFICE CERTIFICATE OF CORRECTION PATENT NO.

DATED lN\/ ENTOR(S) I .1." L I LIJDL ltls certlfled that m appears m are hereby corrected as shown below:

Signed and Sealed this I ninth D3) Of December 1975 [SEAL] Attest:

RUTH C. MASON Arresting Officer 

1. A PROCESS FOR FORMING A STABLIZED LUBRICATING OIL RESISTANT TO OXIDATION AND SLUDGE FORMATION UPON EXPOSURE TO A HIGHLY OXIDATIVE ENVIROMENT WHICH COMPRISES CONTACTING A HIGH BOILING HYDROCARBON FRACTION LUBRICATING OIL STOCK WITH ELEMENTAL SULFUR, SAID SULFUR BEING ADDED IN AN AMOUNT OF FROM ABOUT 0.2 TO ABOUT 1.0 PERCENT BY WEIGHT OF SAID OIL STOCK, SAID CONTACTING INCLUDING A CATALYST MATERIAL SELECTED FROM THE GROUP CONSISTING OF A CRYSTALLINE ALUMINOSILICATE ZEOLITE AN AMORPHOUS SODIUM ALUMINOSILICATE AN OXIDE OF A METAL OF GROUP II-B OF THE PERIODIC TABLE, ALUMINA CONTAINING METALS OF GROUPS VI-B, VIII OR COMBINATIONS THEREOF, ALUMINA CONTAINING A SULFIDE OF A GROUP VIII METAL, AND SILICA, AT A REACTION TEMPERATURE OF FROM ABOUT 130* TO ABOUT 250*C WITH EVOLUTION OF HYDROGEN SULFIDE, SAID CATALYST MATERIAL BEING PRESENT IN AMOUNT OF FROM ABOUT 2 TO ABOUT 15 PARTS BY WEIGHT PER 100 PARTS BY WEIGHT OF SAID OIL STOCK.
 2. The process of claim 1 wherein said oil stock has a boiling range of above about 600*F.
 3. The process of claim 2 wherein said elemental sulfur is present in amount of from about 0.5 to about 0.7 percent by weight of said oil stock, said reaction temperature is from about 150* to about 210*C, and said catalyst material is present in amount of from about 3 to about 15 parts by weight per 100 parts by weight of said oil stock.
 4. THE PROCESS OF CLAIM 1 WHEREIN SAID CONTACTING IS IN THE PRESENCE OF SAID CATALYST MATERIAL IN CONJUNCTION WITH A SECORDARY AGENT SELECTED FROM THE GROUP CONSISTING OF BASES.
 5. The process of claim 4 wherein said base of sodium hydroxide.
 6. The process of claim 1 wherein said oil stock comprises at least a substantial part of one obtained by fractionation of a crude oil identified as Pennsylvania, Midcontinent, Gulf Coast, West Texas, Amal, Kuwait, Barco or Arabian.
 7. The process of claim 2 wherein said oil stock comprises at least a substantial part of one obtained by fractionation of a crude oil identified as Pennsylvania, Midcontinent, Gulf Coast, West Texas, Amal, Kuwait, Barco or Arabian.
 8. The process of claim 1 wherein said oil stock is one obtained by fractionation of crude oil identified as Midcontinent or Arabian. 